A protein product, particularly an isolate, that is highly soluble and produces transparent solutions at low pH would be greatly valued in the food industry for use in various products, particularly beverages, such as soft drinks and sports drinks. The above properties combined with heat stability would further increase the value of the product. Proteins for food use may be derived from plant or animal sources but plant proteins are often less expensive. Soy is a very common source of plant proteins for food use. Soy proteins are recognized for their excellent nutritional properties and health benefits.
Soy protein isolates conventionally are formed by an isoelectric precipitation procedure in which meal from the separation of soy oil from soybeans is processed by an initial extraction under alkaline conditions, before the alkaline extract is acidified to the isoelectric point of soybean protein to result in protein precipitation. The precipitated soy protein may be washed and/or neutralized, then is dried to provide the soy protein isolate. Soy protein isolates have a protein content of at least about 90 wt % (N×6.25) on a dry weight basis (d.b.).
Although a range of soy protein products is available, with a variety of functional properties, to our knowledge, there does not exist a soluble soy protein isolate or product that produces transparent and heat stable solutions under low pH conditions.